Docstrings cleanup

[mattkwiecien]

We don't have a consistent style for our docstrings. This was previously causing warnings in the sphinx auto doc and may be the underlying cause of #384.

Acceptance Criteria

• Decide on either Google or NumPy docstring convention
• Add a linter that we can include in our pre-commit checks (flake8-docstrings seems like it may do the trick)
• Update docstrings to be compliant with whichever convention we choose.